Boeing P-12, F4B refined the art of American biplane fighters

The decade of the 1920s was a transitional time for American military aircraft design and construction.

Early fighters of the era, though better than the machines of the recently concluded Great War, were hardly revolutionary.

They began employing welded steel tube fuselages, a design advancement proven in combat with Fokker fighters flown by German airmen.

The Aircraft Year Book for 1928, reflecting back on 1927, observed: “…the tendency toward the use of metals noted in 1926 was even more marked in 1927. The use of wood fuselage construction has practically disappeared.”

Vintage Boeing P-12 photo depicts aircraft serial number 29-354. This serial was copied for the restoration of the similar Boeing Model 100 now in the Museum of Flight in Seattle. In this photo, the P-12 has streamlined fairings behind each cylinder in an attempt to reduce drag; in actuality, the P-12 gained speed after these fairings were removed. (Boeing photo via Harl V. Brackin, Jr.)

The postwar pursuits initially relied on liquid-cooled engines, even as military planners looked ahead to enhanced simplicity and reliability that could be gained from emerging air-cooled radial powerplants.

Boeing sold a number of biplane fighter designs to the Navy in the 1920s incorporating air-cooled engines, welded steel fuselages, and the use of some corrugated aluminum flight control structure. This was in keeping with the Boeing team’s knack for melding traditional and new technologies as the company hammered out a strong design rationale by the end of the first decade of its existence.

Boeing was not alone in its evolution of fighter design in the 1920s. Curtiss was a strong rival, likewise bridging the divide between air-cooled and liquid-cooled engines in its offerings to the American military.

What followed from Boeing in 1928 began as a privately funded design venture that sought to improve on the performance of those earlier biplanes with lighter weight. Called Model 83, this new biplane initially used a hybrid fuselage construction with welded steel tubing in the forward fuselage and bolted square aluminum tube construction from the cockpit aft.

Boeing employed square aluminum tube in the design of its Model 80 trimotor airliner and in later projects, including B-17 wing structure.

The Boeing Model 83 was called the P-12 by the Air Corps and the F4B by the Navy. It was an early instance of serendipitous commonality — the biplane had been designed to meet a Navy need, but the Air Corps subsequently found it viable for that service’s requirements as well.

P-12s and F4Bs went through a series of model letters. Both services’ examples started out as quite traditional biplanes with fabric-covered fuselages. But with the introduction of the Army’s P-12E and the Navy’s F4B-3, the fuselage was an aluminum-clad semi-monocoque design that foretold the future of fighters.

The handful of Model 100s were civilian test beds, demonstrators, and personal aircraft. One, flown by the Boeing company and registered NC874H, was fitted with a Boeing ring cowl similar to the pioneering British Townend Ring. The cowling reduced drag on this Model 100’s higher compression and supercharged variant of the Pratt and Whitney Wasp engine, and claims of speeds in excess of 200 miles per hour were made for this demonstrator in a January 1930 story in “Aviation” magazine.

Lew Wallick makes the first restoration flight in Model 100 at Boeing Field on 19 September 1977. (Photo by Frederick A. Johnsen)

Production P-12s never breached 200 miles an hour. This Model 100 was later sold to the Mitsui Co. in Japan.

Historian Peter M. Bowers described the P-12 as a fairly safe bet; not too radical to gain acceptance, and with tried-and-true refinements over earlier biplanes to give it a performance edge. Bowers said the P-12 had the good fortune of arriving on the scene when its improvements were valid for the military, just before biplane fighters lost the edge to monoplanes.

The U.S. Army Air Corps, Navy, and Marines flew variants of the P-12 and F4B, as did countries like Thailand and Brazil.

Army P-12E shows the somewhat enlarged fin and rudder common to the Navy’s F4B-3 version. The Navy’s F4B-4 would make the vertical fin even bigger.

The various models of P-12 and F4B evolved different landing gear struts, aileron shapes, fuel tank locations, and, most radically, the aluminum fuselage of the F4B-3, P-12E, and later models.

The National Advisory Committee for Aeronautics (NACA) used a Navy F4B-2 in the first half of the 1930s for a series of explorations on the efficacy of tail configuration changes as an aid to spin recovery.

At one point in the flight research program, the F4B-2 had a T-tail, with its horizontal tail surfaces nearly in line with the biplane’s upper wing, and just over three feet higher than normal position.

This NACA F4B-2 was an early adopter of a spin parachute for emergency recovery, using a design that improved upon a rudimentary and not satisfactory spin chute the Navy had tried earlier.

During spin testing, this Boeing F4B-2 flown by the NACA differed from the standard in having an experimental “T” tail. (NACA)

The T-tail configuration aided spin recovery, according to a NACA report: “The ease with which recoveries could be made was decidedly improved by raising the stabilizer and elevator, especially when the stabilizer and elevator were raised to the top of the fin and rudder. Of all the conditions tested, only the one with the stabilizer and elevator at the top of the fin gave satisfactory recoveries with the controls held neutral.” The larger vertical fin and rudder of the F4B-4 proved helpful in spin recovery.

Fred Johnsen is a product of the historical aviation scene in the Pacific Northwest that has fostered everything from museums to historical publishing. An author, historian, curator and photographer, you can reach him at Fred@GeneralAviationNews.com.

About Frederick Johnsen

Fred Johnsen is a product of the historical aviation scene in the Pacific Northwest that has fostered everything from museums to historical publishing. An author, historian, curator and photographer, you can reach him at Fred@GeneralAviationNews.com.

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